JPH0465925A - Space diversity reception system - Google Patents

Abstract

PURPOSE:To prevent S/N from deterioration by prohibiting the synthesis when a 3rd reception input level is lower than an in-phase synthesis output of two reception input signals. CONSTITUTION:A switching control circuit 1 detects the signal level of a reception input signal C based on the AGC voltage of an AGC amplifier 44 to control the switching of a switch 2. Thus, when the signal level of the signal C is decreased lower than a prescribed level, since the gain of the AGC amplifier 44 is changed to change the AGC voltage, the reduction in the signal level is decided by the voltage to changeover a switch 8, then the reception input signal C is forcibly brought into 0 so that the synthesis of the reception input signal C at a synthesizer 32 is not implemented. Thus, the deterioration in the S/N of the in-phase synthesis output of 1st and 2nd reception inputs is prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a space diversity reception system, and in particular, a combined output signal obtained by combining two reception inputs of two antennas in phase with another antenna. This invention relates to a base diversity reception system in which reception inputs are further combined in phase.

[Conventional technology]

Conventionally, this type of space diversity reception method was
As shown in the figure, the received input signal A is split by a power divider 21, one of which is sent to a power combiner 31, and the other is amplified to a certain level through an AGC amplifier 41 and then input to a phase comparator 51. Ru. After the received input signal B has its phase controlled by an infinite phase shifter (hereinafter referred to as EPS) 11, it is branched by a power divider 22, and
One is sent to the power combiner 31 and combined with the branch output of the received input signal A, and the other is amplified to a certain level by the AGC amplifier 42, and then sent to the phase comparator 51 to be combined with the branch output signal of the received input signal A. They are compared, a voltage corresponding to the phase difference is detected, and the EPS control circuit 61 controls the amount of phase shift of the EPSll according to this phase detection voltage.

Next, the configuration for further in-phase combining the received input signal C with the composite signal obtained by in-phase combining the received input signal A and the received input signal B is almost the same as the above-mentioned configuration. EPS 12 for controlling the phase, the composite signal and the received input signal C whose phase is controlled by 2, respectively.
A power divider 23, 24 that branches, a power combiner 32 that combines the branched signals, and an A that amplifies the branched signals to a certain level.
A phase comparator 52 for obtaining a phase detection voltage by comparing the phases of the outputs of the GC amplifiers 43 and 44 and the AGC amplifiers 43 and 44;
An EPS control circuit 62 is provided to control the amount of phase shift. In this way, it was a space diversity reception system that performed in-phase combination of three reception inputs.

[Problem to be solved by the invention]

In the conventional space diversity reception method mentioned above,
When the reception level of receiver power C is low, a signal with degraded S/N is superimposed on the in-phase combined signal of receiver power A and B, so that in the in-phase combined signal of receiver power A and B,
If the reception level of at least one of the reception input levels A and B is high and the S/N of the in-phase composite signal is good as a result, the deterioration of the S/N due to the combination of the reception input level C is small, but the reception input level If both A and B are low and as a result, the S/N of the in-phase composite signal becomes poor, the noise level added in the synthesis of the receiver's human power C becomes relatively large with respect to the signal level, and the S/N becomes worse. There was a drawback that N deteriorated rapidly.

[Means to solve the problem]

The space diversity reception method of the present invention is characterized in that among the received signals input from three antennas, the first and second
a first infinite phase shifter for controlling the phase of one of the received signals in order to combine the received signals in the same phase; and a first power combiner for combining the first and second received signals in the same phase. and a second infinite phase shifter that controls the phase of the third received signal so that it is in phase with the combined signal of the first power combiner, and the phase is controlled by the second infinite phase shifter. and a second power combiner that combines the signal obtained by combining the signal and the composite signal.
a level detection section A, a switching control circuit that outputs a first or second switching signal, respectively, depending on whether the detection level of the AGC level detection section A is higher or lower than a predetermined threshold; The first and second switching signals cause the second
and a switch that combines the output of the infinite phase shifter and the output of the second power combiner, respectively, or terminates the output with a terminator.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, and the same parts in FIG. 1 as in FIG. 2 are given the same reference numerals. 1st
The embodiment shown in the figure has a switching control circuit 1 and a switching device 2, compared to the conventional in-phase synthesis three-plane space diversity reception system.
It has

In this embodiment, the reception signal C itself is phase-controlled by the EPS 12 and then combined by the power combiner 32, and the branch output signal of the power divider 23 which is input to the power combiner 32 and the power divider 24 The branch output signals of
A switch 2 is provided to switch between two conditions: terminating at 1.92. The switching control circuit 1 is an AGC amplifier 44
The signal level of the received input signal C is detected from the AGC voltage of , and the switching of the switch 2 is controlled. As a result, when the signal level of the received input signal C decreases below a certain level, the gain of the AGC amplifier 44 changes and the AGC voltage changes, so a decrease in the signal level is determined based on this voltage value. Then, the switch 8 is switched to force the signal on the received input signal C side to be 0 so that the synthesizer 32 does not combine it with the received input signal C side.

Note that, as described above, when at least one of the reception input levels A and B is high, even if the reception inputs whose reception input level C is low are combined, the S/N of the combined output signal does not deteriorate much. Therefore, as shown by the dotted line in FIG.
When the AGC detection voltage is higher than a certain threshold value, a three-sided combination state, that is, a system in which the switch 2 is continuously connected to the combination side is also possible.

〔Effect of the invention〕

As explained above, the present invention provides two reception input signals A,
When combining the third reception input signal C with the in-phase combination output of H, by not performing the combination when the third reception input level C is low, the third The S/N ratio of the in-phase composite output of the first and second receiving inputs is degraded by adding the received input signal itself and the noise generated in the path from the third receiving input to the combiner input. It has the effect of preventing

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional space diversity reception system. 1... Switching control circuit, 2... Switching device, 11.12.
・・Infinite phase shifter (EPS), 21, 22, 23.24・
...Power divider, 31.32...Power combiner, 41°42.43.44...AGC amplifier, 51.52...
・Phase comparator, 61.62...EPS control circuit, 91
゜92...Terminator.

Claims (1)

[Claims] A first infinite antenna for controlling the phase of one of the received signals inputted from the first and three antennas in order to combine the first and second received signals in the same phase. a phase shifter; a first for combining the first and second received signals in phase;
a power combiner, a second infinite phase shifter that controls the phase of the third received signal so that it is in phase with the combined signal of the first power combiner, and the second infinite phase shifter. AGC level detection for detecting high or low output level of the second infinite phase shifter in a space diversity reception system having a second power combiner that combines a phase-controlled signal and the composite signal. A switching control circuit that outputs a first or second switching signal depending on whether the detection level of the AGC level detection section A is higher or lower than a predetermined threshold; A space diversity reception system characterized by comprising a switch that combines the output of the second infinite phase shifter and the output of the second power combiner or terminates the output with a terminator using a second switching signal. . 2. Input the detection voltage D of the AGC level detector B for detecting the level of the output level of the first power combiner to the switching control circuit, and use the information of the AGC level detectors A and B to When the detection voltage D is high, the first
Claim 1 characterized in that the switching signal continues to be transmitted.
Space diversity reception method described.